1. Field of the Invention
This invention relates generally to a non-metallic device and method for the stabilization of at least a portion of a vertebral column and more particularly to a device and method for spinal stabilization without fusion.
2. Description of the Prior Art
Fusion of vertebral columns by instrumentation devices and/or bone material is common and a long practiced surgical technique. Fusion is the permanent internal fixation of part or all of the intervertebral joints, an intervertebral joint being composed of two adjacent vertebrae and their posterior bony elements connected by an intervertebral disc, ligaments, and two facet joint capsules. However, the concept of fusion carries significant and previously unappreciated patient disability. By fusing vertebrae the remaining segments are subject to inordinately high stress and degeneration. In the typical L4-S1 fusion the L3-4 level typically undergoes dramatic degeneration of the disc and zygoapophyseal joints leading to the production of a clinical entity called the "transitional syndrome" often leading to "mechanical-type" pain or actual spinal nerve compression. The stress patterns produced by fusion often produce clinical problems relating to the sacro-iliac and hip joints.
When spine fusions involve mechanical instrumentation, significant forces are directly aimed at the supportive sites whether they be bone screws, hooks, etc. This phenomenon usually produces loosening of the points of attachment for the implanted hardware and a resulting loss of support by this instrumentation. Because of this, fusions involving instrumentation are often carried out in conjunction with a bone fusion so as the instrumentation loosens and fails, support can be maintained by growth of the bony counterpart. These combined procedures involve extensive surgery, substantial blood loss and high cost. Following such a procedure, patients are usually disabled for long periods of time.
Therefore, the treating of spinal instability by fusion is not optimal. It immobilizes adjacent segments, eliminating their previous natural ability to move relative to each other. Further, when fusion has taken place with the addition of internal fixation, often the internal fixation parts are of a metallic nature. In modern medical practice the presence of dense metallic devices is a significnat liability due to the scattering artifacts generated if imaging is attempted. Since the spinal diagnostic procedure of choice is imaging, the presence of significant metallic objects represents a serious diagnostic limitation.
The present invention addresses the problems associated with the prior art devices and method for treating spinal instability and provides for stabilization, rather than fusion, that is, support with the allowance of some natural movement or flex, and accomplishes this with a minimal amount of metallic components.